We can make a very good estimate of the height of the person in the tooth-soot by comparing it to the gentleman passing by on his right, who fortuitously is nearly exactly the same distance from the camera (we also could have triangulated on the door behind, if necessary).

Our subject comes up to the bridge of Mr. Pedestrian's nose. Assuming that this fellow is a North American male of average height (70"), that would make the costumed cuspid about 4-5 inches shorter - ie, about five and half feet tall, and well within the reasonable range for a typical adult, male or female.

You seem to be assuming that the human in the costume has his arms up, when he has his upper arms down and close to the body and only bent out at the elbow - "tight-in jazz hands" style. The top of his/her head is right up at the top of the costume. Unless the guy on the left is waaay shorter than he appears, I am confident in my estimate.